Apparatus for developing sound track motion picture film



Jan. 1, 1935. s. R. HElsLER APPARATUS FOR DEVELOPING SOUND TRACK MOTIONPICTURE FILM Filed July 29, 195o z sheets-sheet 1 (ji-f. [06

, /0 62 6,65 Il l ,q q 7 '5 g I6 5 I8 qq 50 75 88 Jan. 1, 1935. s. R.HElsLER 1,986,107

APPARATUS FOR DEVELOPING SOUND TRACK MOTION PICTURE FILM Filed July 29,1930 2 Sheets-Sheet 2 E g 5 /N VEN TOR @XM/@IMM Patented Jan. 1, 1935UNITED STATES APPARATUS FOR DEVELOPING SOUND TRACK MOTION PICTURE FILMStuart Raymond Heisler, Los Angeles, Calif., assignor to Fred Hotohner,Los Angeles, Calif.

Application July 29, 1930, Serial No. 471,547

9 Claims.

This invention relates to an apparatus for developing sound track motionpicture nlm and the main object thereof is to produce a positive iilmready for exhibition purposes having two parallel tracks of photographicimpressions, one track being of motion pictures and the other being aseries of impressions from which the sound accompaniment may bereproduced by suitable apparatus, each of said tracks being developed toa different gamma.

In the production methods now generally used independent control can beexercised over each step of the process of producing the photographicimpressions of the sound and picture tracks up to that point in theprocess where the development `of the release print takes place. Thegeneral practice is to print each track of impressions onto the positivefilm from separate negatives while the opposite track is masked off andthen to run the film carrying the latent images of both tracks thru thedeveloping machine in which both tracks receive identical treatmentafter which the nlm is dried and reeled.

Apparatus for exhibiting the production permits independent control overthe output from the two tracks of developed impressions. Thus in theentire series of operations in the process of lming a show andexhibiting the same the only step in which the operation on the twotracks of impressions is interdependent in the present general practiceis the step of developing the release print.

l Because of this single fact, that the two tracks must under thepresent nlm laboratory practice receive identical treatment in thedevelopment of the release print, serious limitations are imposed on allof the operations leading up thereto and compromises must be made topermit compliance with this requirement. The cost of production isincreased over what it would be were independent control exercised overthe processing of the two tracks through the entire production and thequality of the effects secured is impaired. as it is necessary tosacrice part of the possible results that could otherwise be secured.

In the development of photographic record on iilm the controllingfactors are expressed by a sensitometer curve in which the log. exposureis plotted against the density of the developed nlm given any one valueof the length of time in the developer. The exposure is the product ofthe intensity of the light and the time it has been applied. For eachvalue of the length of time in the developer a different curve may bedrawn. The tangent of the angle made by the straight portion of thecurve and the abscissa of the coordinate system is known as the gamma towhich the film has been developed. In a nlm developed to a gamma of onethe contrast of the im is considered to be equivalent to brightnesscontrast ci the scene. A value of gamma greater or less than oneindicates that the contrast of the `hlm is greater or less than thecontrast of the scene. The product or" the negative gamma and thepositive gamma is termed the over-all gamma. For the best production oibrightness relationships the over-all gamma should be equal to unity. Asa practical matter in the production of motion pictures a value ofslightly greater than unity is used to allow for losses of detail in theprojection apparatus.

In the production of the picture track a different set of conditionsprevail than in the production of the sound track and from an artisticviewpoint different result are looked for by different photographers.Because of artistic considerations the picture negative is usuallydeveloped to a much less than one and the positive to a gamma greaterthan one. An average set of values considered to be a gamma o 0.55 orthe negative and 2.00 for the positive giving an over-all gamma of 1.10.However these values are discretionary and it is desired that theproducer may be able to vary them at will.

A positive nlm developed to a gamma of 2.00 has a greater average ofdensity values than a film developed to a gamma of one, hence in thereproduction of sound from such a nlm it is necessary to make use of avery intense source or" light to get the equivalent reproductioncurrents in the sound apparatus to that which could be secured by theuse of film having a sound record suitably exposed and developed to agamma oi' one. Not only does this mean a loss oi power but it introducesmechanical complications as there is a practical limit to the amount oflight that may be developed and transmitted thru the very smallapertures of sound apparatus.

The most serious drawback in the prior art practice however, is that inorder to provide a picture track of the quality which the public haslearned to expect harmonic distortion is produced in the sound recorddue to the limitations imposed upon the filming thereof by the fact thatr in the release print both tracks must be developed to the same gamma.The explanation of this is as follows:

The projection of the straight portion of the characteristicsensitometer curve of any particular film stock upon the abscissa of thecoordinate system is termed the latitude and indicates the range ofvalues over which the exposure may be varied and be faithfullyrepresented by the resulting developed images. I rind that the latitudedecreases with the increase in gamma and that the distortion which isnow common in such records is due to the fact that the exposure valuescan not be held within the latitude when a gamma of much greater thanone is selected. Therefore this invention provides for the use of thatvalue of gamma for both negative and positive films which allows thegreatest range of values of the exposure in both the negative andpositive ilms.

Thus we see that for the securing of the best results from both thesound track and the picture track they must be developed to diierentgamma values. In the case of the picture track a considerable differenceis indicated as necessary between the gamma of the negative and of thepositive lms and in the case of the sound track I have discovered thatthe most suitable set of values with present lm stocks is a gamma of onefor both negative and positive. While it is necessary in the case of thepicture track to have an over-all gamma of something over unity to allowfor dispersion in the lens system, on the screen and from various otherfactors in projection, this condition need not be observed in theselection of the over-all gamma of the sound track. In fact it appearsthat a value of unity is clearly indicated as most eiiicient andsatisfactory for the sound track.

In general the object of the invention is to provide a simple andeiiicient means for developing a iilm of the type described in twostages. In the rst stage the iilm is immersed in the developing bathonly suiiicient to wet and develop the images of one of the two tracks.In the second stage the nlm is completely submerged in the bath and thedevelopment of both tracks takes place together, the track that wasIirst immersed thus being developed for a longer period of time isdeveloped to the higher gamma. Usually this further object of theinvention is to provide a simple and rapid means of varying the ratio ofthe lengths of lm threaded thru the two sections of the machine in whichthe two stages of development take place. Since in practice variousdifferent pieces of lm are run thru the machines in commercial lmlaboratories from different productions which in using this inventionwill be specified for development for times having different ratios, itis a further object to provide means for changing this ratio while thenlm is in motion without interrupting the iow of work thru the machineand without taking up or letting out slack lm at any point.

A further object is to provide means for preventing the solution fromclimbing up onto that portion of the lm which is out of the bath in therst stage of the development.

Further objects will become apparent from the following description.

An embodiment of the invention is illustrated in the accompanyingdrawings, but it is to be understood that this invention is not limitedto the particular type of apparatus shown, as without departing from thespirit of the invention it may be embodied in numerous ways within thepurview of the claims.

Figure 1 is a longitudinal sectional View thru a tank in which iscontained the mechanism for traversing the film thru the bath, the bathbeing shown submerging the mechanism up to the division line of the twotracks of the film in the first stage of the developing process.

Figure 2 is a plan View of the machine shown in Figure l.

Figure 3 is a cross section thru a lm enlarged to show how a nlm may beprepared to reduce the tendency of the developing solution climbing ontothe upper track of the nlm in the first stage of the development.

Figure 4 is a perspective View of the mechanism with a length of nlmthreaded thru it to illustrate more clearly the general relation of thevarious elements.

Figure 5 is a View of a section of nlm shown partly submerged in thebath in the nrst developing position .in the machine showing theposition of the surface of the bath in relation to the two tracks ofphotographic impressions.

In the drawings, numeral 1 indicates the tank in which is the developingbath 2 and a machine 50 for traversing the nim 3 thru the bath. Thevarious elements are not shown in true proportion, being exaggeratedwhere necessary in order to more clearly illustrate the generalarrangement and the relation of the various elements to each other. Itis particularly to be noted that the two lengths of nlm 4 and 5 inpractice are much greater than indicated in the views and that theproportion of the lengths of lm in the loops 6 and 7 is so small as t0be negligible.

The nlm enters the machine at 9 runs between the sprocket 10 and theidler 11, passes thru the loop 6 to the sprocket 12 and idlers 13 and 13and then in a vertical plane it travels over the stretch indicated by 4partly submerged in the bath. At the end of the stretch 4 the nlm passesbetween the sprocket 14 and idler 15 and thence thru the loop 7 becomingcompletely submerged in the bath and after passing between the sprocket16 and the idler 17 travels over the stretch 5 to the sprocket 18, thenrises out of the bath to the sprocket 19 and leaves the machine asindicated at 20 to the next units in the plant to be washed, fixed,dried and reeled.

lThe sprockets are all driven at the saine speed so that the nlm ismaintained taut in the same relative positions as it passes thru themachine. The sprocket 10 is driven thru the right hand helical gear set21-22 by the shaft 23 on which is mounted the sprocket l2. The sprocket14 is driven by the shaft 24. The sprocket 16 is driven thru the lefthand gear set 25-26 by the shaft 27. The sprockets 18 and 19 are driventhru the right hand spiral gear sets 28-29 and 30-31 by the shaft 32.The shafts 23, 24, 27 and 32 are driven respectively by the worm gears33, 34, 35 and 36 having a pitch diameter equal to the diameter of thesprockets plus the thickness of the nlm. All of the worm gears are ofthe same pitch diameter. All of the sprockets are of the same diameter.All of the helical gear sets have a one-to-one ratio.

The worm gears are driven by the worm shaft 37. Thus as the peripheralspeed of all of the sprockets is the same, the lengths of film betweenthe sprockets remain constant as the iilm passes thru the machine.

The mechanism is made in assemblies 51, 52 and 53.

three sections, the The assemblies are connected together in operationby the worm shaft 37, the screw shaft 54 and the smooth shaft v55. Theassembly 51 starts the film thru the bath in Va lpartially submergedposition. The assembly y52 turns the film over, completely submergingthe same. The assembly 53 directs the film out of the bath.

The assembly 51 includes the frame 56 which is secured to the wall v57of the tank 1, the bearu ings 5.8, 59 and 120 thru which extends theshaft l23, the bearings 60 and 61 thru which extends the shaft 62 onwhich is mounted the gear 21 and the sprocket 10, and the arms 65, 121and 122 which `carry the idlers 1l, 13 and 13. The stuffing boxes 63 and64 formed with the frame 56 provide means for the shaft 54 and the wormshaft 37 to extend outside of the tank.

The assembly 52 is adjustable lengthwise in the tank and may bemovedbackwards and forwards without giving or taking slack in any part of theiilm either while the machine is still or while the film is in motion,This is accomplished by turning the hand wheel 66 thus moving the frame67 by virtue of the internal threads in the sleeve 68, The smooth boredsleeve 69 slides along the shaft `55 which maintains the assembly in itscorrect position with respect to the worm shaft and the nlm. It is to benoted that the worm gears 34 and 35 being on opposite sides of the wormshaft equalize each other in thrust and thus the Worm shaft needs nosupport from bearings other than at the ends of the tank. The frame 67includes the bearing 70 thru which passes the shaft 127 on which aremounted the gear 25 and the sprocket 16, the bearings 72 and 73 thruwhich passes the shaft 24, the bearings 74 and 75 thru which pass theshaft 27, the arms 76 and 77 which carry the idlers 15 and 17, and theframe members 78, 79, .80, 81, 82, 83, 84, and v86 which connect thevarious bearings together.

The assembly 53 includes the frame 87 which is secured to the end 88 ofthe tank 1. The ends of the shafts 54, 55 and 37 fit into suitablebearings as indicated at 89, 90 and 91. The screw shaft 54 is positionedby the collars 107 and 108. The worm shaft 37 is positioned by thecollars at the two .ends of the machine and 106 at opposite ends and isdriven by any suitable means from the end 109. The frame includes thebearings 92 and 93 thru which pass the shafts 94 and 95 respectively,which carry the gear and sprocket sets 28e-18 and 30-19 respectively;the vbearings 9 6, 97 and 98 thru which the shaft 32 extends; and theframe members 99, 100, 101, 102, 103` and 104 which connect the variousbear ings together.

In threading the film thru the machine the emulsion side is turned awayfrom the sprockets. As the film passes over the stretch indicated by 4it is desi-red that only onel of the tracks of latent images be incontact with the developer. The results of the process are not extremelycritical as to this requirement for if a small amount of developmentdoes take place on the upper track the quality is only slightly lowered.However for the best results care must be exercised in constructing theapparatus to avoid climbing of solution onto the emulsion side iof theupper part of the film at the sprocket 12. To this end the two idlers 13and 13' have been here shown instead of a single idler. However at 15 itis immaterial if solution climbs up the idler and wets the top of thefilm inasmuch as the film is completely submerged immediately afterpassing by the idler.

In Figure 5 I have shown the relation of the surface of the bath to thetwo tracks of latent images in the first stage of development. Numeral38 indicates the track of picture records and 39 the track of soundrecords and 40 the surface of the bath.

I have found that climbing of solution during the time that the film ispassing over the stretch 4 by capillary action can be prevented byproviding the film with a discontinuity of the emulsion surface. Thismay best be done by making a scratch thru the emulsion down to thecelluloid. In Figure 3 a cross section of a film is shown so devised.The emulsion side of the film is indicated by 42 and the scratch by 43.If the scratch is deep enough to expose the Celluloid as at 44 theprobability of solution climbing is very small as the Celluloid is notwetted by the solution. As a practical matter the apparatus should beadjusted so that the scratch is just above the surface of the bathrather than to attempt to make the two coincide.

Thus while I have described my invention in detail and with respect to apreferred embodiment thereof, I do not desire to be limited te thespecific apparatus shown or the particular arrangement of parts insofaras permissible modifications under the broad ideas disclosed are con- Icerned, since many changes and modiiications thereof are possible andthe invention may be embodied in widely varying forms without departingfrom the spirit and scope thereof in its broader aspects. Hence I desireto include all modifications and arrangements coming within the languageand scope of any one or more of the appended claims.

Having thus described my invention, what I claim is:

l. In an apparatus for developing sound track motion picture filmcontaining two parallel tracks of latent photographic impressions eachof which is to be developed to a different gamma, a tank adapted tocontain a developing bath and means to traverse said film thru said bathin one opera tion in two stages, each length of said iilm beingmaintained substantially in a vertical plane and immersed onlysufficient to wet that one of the two tracks of latent images which isto be nnally developed to the higher gamma in the first of said stages,there being means to alter the position of said film with respect to thesurface of said bath at the end of the first stage and to completelyimmerse said film whereby both said tracks of latent images aredeveloped together in the second of said stages.

2. In an apparatus for developing sound track motion picture film, atank adapted to contain a developing bath, mechanism fixed with relationto said tank and located at one point of the surface of said bath todirect a lm into said bath and start the same traveling thru said bathpartly submerged in the same, mechanisi fixed with relation to said tankand located at another point of the surface of said bath to receive saidfilm after it has traveled a distance thru said bath partly submergedand to alter the position thereof with respect to the surface of saidbath so that it becomes completely submerged in said bath and to startthe same traveling farther thru said bath completely submerged, andmechanism fixed with relation to said tank and located at a third pointof the surface of said bath to receive said film after it has traveled adistance thru said bath completely submerged and to direct the same outof said bath.

3. In an apparatus for developing sound track motion picture iilm, atank adapted to contain a developing bath, mechanism fixed with relationto said tank and located at one point of the surface of said bath todirect a iilm into said bath and to start the same traveling thru saidbath partly submerged in the same, mechanism fixed with relation to saidtank and located at another point of the surface of said bath to receivesaid iilm from a position of complete submergence and to direct the sameout of said bath, and mechanismixed with relation to said tank so as tobe adjustable along the line of travel of said lm thru said bath toalter the position of said film with respect to the surface of said bathfrom a position of partial submergence to a position of completesubmergence.

4. In a lm developing machine, in combination, a tank adapted to containa developing bath, mechanism fixed with relation to said tank andincluding a sprocket positioned in proximity to the surface of said bathand disposed to traverse a film thru said bath partly submerged therein,a second sprocket similarly disposed with respect to the surface of saidbath and spaced from the first said sprocket, and a third sprocketdisposed in proximity to the first said sprocket and so positioned withrespect tothe same that a nlm looped between both said sprockets maytravel from a point outside of said bath over the third said sprocket,thru said loop and around the rst said sprocket and then thru said bathpartly submerged therein to the second said `sprocket, means to maintainsaid iilm in contact with said sprockets in the manner described andmeans to drive all of said sprockets together at the same peripheralspeed.

5. In a film developing machine, in combination, a tank adapted tocontain a developing bath, mechanism fixed with relation to said tankincluding a sprocket positioned in proximity to the surface of said bathand disposed to traverse a film thru said bath partly submerged therein,there being means to traverse said iilm from a point outside of saidtank to said sprocket and means to maintain said film in engagement withsaid sprocket, another sprocket similarly positioned with respect to thesurface of said bath and disposed to receive said lm after said lm hastraveled thru said bath partly submerged therein, said second sprocketbeing adjustable along the line of travel of said iilm thru said bath,and means to drive both said sprockets at the same peripheral speed,said driving means lbeing geared to add or to subtract an amount ofperipheral movement to the movement of the second said sprocket exactlyequal to the lineal movement away from or towards said iirst sprocket inadjustment along the line of travel of said iilm.

6. In a lm developing machine, a tank adapted to contain a developingbath, mechanism fixed with relation to said tank and including avertical shaft, a sprocket on said shaft disposed to move a film thrusaid bath in a. vertical plane and partly submerged therein, said shaftcontinuing upwards and driving a second shaft in a horizontal plane thrusuitable gears, there being another sprocket on said horizontal shaft,the diameters of said sprockets and the ratio of said gears being suchthat both said sprockets turn, when driven, at the same peripheralspeed, and suitable means to maintain a iilm in contact with saidsprockets and looped over the top of said second sprocket and partiallyaround the first said sprocket in engagement with the teeth thereof,whereby upon a film being threaded in said manner thru said device andthe same being driven in the proper direction, said film will pass overthe upper of said sprockets, thru said loop, and around the lower ofsaid sprockets, and thence thru said bath in a partly submerged positionrunning continuously as long as driven without taking or giving slack insaid loop.

7. In a film developing machine, a tank adapted to contain a developingbath, means to start a film traversing thru said bath in a verticalplane and partly submerged therein and a carriage adjustable along theline of travel of said iilrn thru said bath and having a verticalsprocket to receive said film as it approaches said carriage in avertical plane and partly submerged and another sprocket located withthe axis thereof in a horizontal plane and the lower part thereof beingbelow the surface of said bath, both said sprockets being driventogether and at the same peripheral speed so that a film looped aroundthe first said sprocket and under the second said sprocket will passthru said carriage without taking or giving slack in said loop whendriven, there being means to keep said film in engagement with the teethof said sprockets, and means to adjust said carriage along the line oftravel of said film and at the same time to add or to subtract to theperipheral speed of said sprockets just suiiicient to take up or givevout a length of iilm equal to the linear change in position of saidcarriage along the line of travel of said nlm.

8. In a machine for developing sound track motion picture film, a tankadapted to contain a bath of developing solution, means for traversing afilm thru said bath in a vertical plane and partly submerged for aportion of the length of the travel of said lm thru said bath and meansfor twisting said film over into a horizontal plane and traversing thesame thru a loop whereby the lm becomes completely submerged for theremainder of the distance of its travel thru said bath.

9. In an apparatus for developing sound track motion picture filmcontaining two parallel tracks of latent photographic impressions one ofwhich is to be developed tor a different gamma than the other, a tankadapted to contain a developing bath, means to guide said film incontinuous traverse from outside the tank into the bath and thru saidbath in a partially submerged condition for the rst part of its travelthru said bath to start the development of one of said tracks of images,and means to alter the position of said lm with respect to the surfaceof said bath at the end of said first portion of travel so that saidfilm is completely submerged in said bath for the remainder of itstravel thru said bath. and means to guide said film out of said bath atthe end vof its travel therethru.

STUART RAYMOND HEISLER.

